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BackgroundAtrial fibrillation has an estimated prevalence of 1.5–2%, making it the most common cardiac arrhythmia. The processes that cause and sustain the disease are still not completely understood. An association between atrial fibrillation and systemic, as well as local, inflammatory processes has been reported. However, the exact mechanisms underlying this association have not been established. While it is understood that inflammatory macrophages can influence cardiac electrophysiology, a direct, causative relationship to atrial fibrillation has not been described. This study investigated the pro-arrhythmic effects of activated M1 macrophages on human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes, to propose a mechanistic link between inflammation and atrial fibrillation.MethodsTwo hiPSC lines from healthy individuals were differentiated to atrial cardiomyocytes and M1 macrophages and integrated in an isogenic, pacing-free, atrial fibrillation-like coculture model. Electrophysiology characteristics of cocultures were analysed for beat rate irregularity, electrogram amplitude and conduction velocity using multi electrode arrays. Cocultures were additionally treated using glucocorticoids to suppress M1 inflammation. Bulk RNA sequencing was performed on coculture-isolated atrial cardiomyocytes and compared to meta-analyses of atrial fibrillation patient transcriptomes.ResultsMulti electrode array recordings revealed M1 to cause irregular beating and reduced electrogram amplitude. Conduction analysis further showed significantly lowered conduction homogeneity in M1 cocultures. Transcriptome sequencing revealed reduced expression of key cardiac genes such as SCN5A, KCNA5, ATP1A1, and GJA5 in the atrial cardiomyocytes. Meta-analysis of atrial fibrillation patient transcriptomes showed high correlation to the in vitro model. Treatment of the coculture with glucocorticoids showed reversal of phenotypes, including reduced beat irregularity, improved conduction, and reversed RNA expression profiles.ConclusionsThis study establishes a causal relationship between M1 activation and the development of subsequent atrial arrhythmia, documented as irregularity in spontaneous electrical activation in atrial cardiomyocytes cocultured with activated macrophages. Further, beat rate irregularity could be alleviated using glucocorticoids. Overall, these results point at macrophage-mediated inflammation as a potential AF induction mechanism and offer new targets for therapeutic development. The findings strongly support the relevance of the proposed hiPSC-derived coculture model and present it as a first of its kind disease model.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13287-024-03814-0.

SummaryThe cornea and sclera are distinct adjacent tissues, yet their stromal cells originate from common neural crest cells (NCCs). Sclerocornea is a disease characterized by an indistinguishable boundary between the cornea and sclera. Previously, we identified a RAD21 mutation in a sclerocornea pedigree. Here, we investigated the impacts of RAD21 on NCC activities during eye development. RAD21 deficiency caused upregulation of PCDHGC3. Both RAD21 knockdown and PCDHGC3 upregulation disrupted the migration of NCCs. Transcriptome analysis indicated that WNT9B had 190.9-fold higher expression in scleral stroma than in corneal stroma. WNT9B was also significantly upregulated by both RAD21 knockdown and PCDHGC3 overexpression, and knock down of WNT9B rescued the differentiation and migration of NCCs with RAD21 deficiency. Consistently, overexpressing wnt9b in Xenopus tropicalis led to ocular developmental abnormalities. In summary, WNT9B is a determinant factor during NCC differentiation into corneal keratocytes or scleral stromal cells and is affected by RAD21 expression. Graphical abstract Highlights•Established a stable differentiation protocol from hESCs to corneal keratocytes•RAD21 deficiency affected the proliferation and migration ability of NCCs•Increased scleral markers after RAD21 knockdown during NCC differentiation to cornea•WNT9B is a crucial mediator during ocular NCC differentiation Cell biology; Developmental biology

Cytosine base editors (CBEs) revolutionize genome editing by enabling precise C-to-T conversions without double-strand breaks. Sdd7, a recently developed cytosine deaminase, exhibits high activity across a broad protospacer range but induces unintended off-target effects, including bystander mutations within and upstream of the protospacer and both gRNA-dependent and independent deamination. Here, we report that BE4max and Sdd7 induce bystander editing upstream of the protospacer. To overcome this, we engineer two Sdd7 variants, Sdd7e1 and Sdd7e2, enhancing specificity while preserving on-target efficiency. These variants display reduced bystander editing, narrowed editing windows, and significantly lower off-target activity. Delivery as ribonucleoproteins via engineered virus-like particles (eVLPs) further improves specificity, nearly eliminating bystander edits and increasing precise single-point mutations. Our findings establish Sdd7e1 and Sdd7e2, especially when delivered via eVLP, as high-fidelity CBEs poised for safe, precise therapeutic genome editing. CRISPR base editors enable precise DNA changes but often cause off-target edits. Here, authors engineer two Sdd7 variants that minimize bystander and off-target mutations and show enhanced precision when delivered as ribonucleoproteins via engineered virus-like particles.

Single-cell technologies can measure the expression of thousands of molecular features in individual cells undergoing dynamic biological processes. While examining cells along a computationally-ordered pseudotime trajectory can reveal how changes in gene or protein expression impact cell fate, identifying such dynamic features is challenging due to the inherent noise in single-cell data. Here, we present DELVE, an unsupervised feature selection method for identifying a representative subset of molecular features which robustly recapitulate cellular trajectories. In contrast to previous work, DELVE uses a bottom-up approach to mitigate the effects of confounding sources of variation, and instead models cell states from dynamic gene or protein modules based on core regulatory complexes. Using simulations, single-cell RNA sequencing, and iterative immunofluorescence imaging data in the context of cell cycle and cellular differentiation, we demonstrate how DELVE selects features that better define cell-types and cell-type transitions. DELVE is available as an open-source python package: https://github.com/jranek/delve. Characteristic genes or proteins driving continuous biological processes are difficult to uncover from noisy single-cell data. Here, authors present DELVE, an unsupervised feature selection method to identify core molecular features driving cell fate decisions.

Current approaches to the treatment of schizophrenia have mainly focused on the protein-coding part of the genome; in this context, the roles of microRNAs have received less attention. In the present study, we analyze the microRNAome in the blood and postmortem brains of schizophrenia patients, showing that the expression of miR-99b-5p is downregulated in both the prefrontal cortex and blood of patients. Lowering the amount of miR-99b-5p in mice leads to both schizophrenia-like phenotypes and inflammatory processes that are linked to synaptic pruning in microglia. The microglial miR-99b-5p-supressed inflammatory response requires Z-DNA binding protein 1 (Zbp1), which we identify as a novel miR-99b-5p target. Antisense oligonucleotides against Zbp1 ameliorate the pathological effects of miR-99b-5p inhibition. Our findings indicate that a novel miR-99b-5p-Zbp1 pathway in microglia might contribute to the pathogenesis of schizophrenia. Synopsis The involvement of microRNAs in the pathogenesis of schizophrenia is not well-understood. This study shows that miR-99b-5p regulates Z-DNA binding protein 1 (Zbp1) to control inflammatory responses in microglia and the development of schizophrenia-like symptoms in mice. miR-99b-5p is downregulated in the blood and brains of schizophrenia patients.miR-99b-5p inhibition induces schizophrenia-like phenotypes in mice and microglial inflammation.Zbp1 is a novel miR-99b-5p target in microglia.Zbp1 antisense oligos ameliorate the pathological outcomes of decreased miR-99b-5p levels. Dysregulation of a novel miR-99b-5p-Zbp1 (Z-DNA binding protein 1) pathway in microglia induces inflammatory responses and schizophrenia-like phenotypes in mice.